510 
DR. WILLEMS. 
duced by culture, according to the admirable methods of Mr. 
Pasteur. 
Exudative pleuro-pneumonia also proceeds from an inferior 
organism, which is the agent of its transmission, and which can 
be reproduced. This affection must, consequently, take rank in 
the class of parasitic diseases. 
I desire here to recall the fact that in 1850, in my first paper? 
I stated that Prof. Yan Kempen and myself had found in the 
exudates of pleuro-pneumonia and in those of the pustules or 
tumefactions following its inoculation, a corpuscle, with a pecu¬ 
liar motion and which exists only in this affection, but whose sig¬ 
nification at that time was unknown to us. 
Now, guided and enlightened by the discoveries of our con¬ 
temporaries, and especially those of Mr. Pasteur, I have resumed 
the study of these corpuscles, which thirty years ago had aroused 
my attention and curiosity, and after new investigations, I think 1 
can affirm that it is a true parasite. 
In my preceding researches, I had established that the power 
of contagion resides in the expired air from the lungs of a sick 
animal, and in the exudate which is found in the interlobular 
tissues of these orgaus. Subsequently, I found that the germ 
corpuscle is met with in almost all the tissues and fluids of the 
sick animal. It is seen in abundance in the lung, the effused 
fluid of the pleura, and the pathological products of the intes¬ 
tines, of the liver, &c. It is in small quantities in the blood and 
muscles ; but still, in these last sufficiently discoverable to allow 
one to recognize the meat of a pneumonic animal. 
In my studies upon the nature of the parasite, I have had in 
view not only a purely scientific object, but have hoped to reach, 
also, one of practical utility, in determining which is the most 
convenient matter to inoculate; from what part the virus ought 
to be taken, and how, and during how long a time it can be pre¬ 
served. 
Experiments will also be made with a view to obtain a culti¬ 
vated and weaker virus, as Mr. Pasteur has done for chicken 
cholera, and thus obtain for inoculators a sure and efficacious 
virus. 
